1. Field of the Invention
The present invention relates to the optimization of read/write channel parameters in a magnetic disk recording device such as a hard disk drive, and in particular, to techniques for optimizing write channel parameters as well as read channel parameters in accordance with head/zone combination characteristics.
2. Description of the Related Art
A read/write channel encodes write data received from a host computer and outputs the encoded write data to a head, prior to writing the data on a disk. It also decodes data read from the disk and transmits the read data to the host computer. Thus, the read/write channel circuit is a significant factor in determining the data read/write performance. In general, interpretation of an analog signal retrieved from a disk or writing specific data on the disk varies with channel parameter settings for the read/write channel circuit. That is, an error rate during a data read/write operation changes depending on channel parameters.
In this context, a hard disk drive manufacturer determined read/write channel parameters from experiments on several drive samples and applies the determined parameters commonly to all drives. The differences of characteristics of each drive brought about a large difference between the error rates of drives and high error rates, so as to lower the data reproduction capability of a drive. To circumvent this problem, many read channel parameter optimization techniques have been explored. Read channel parameters include the cut-off frequency, filter boost, threshold voltage, and window shift of a read/write channel circuit for use in processing a read signal during reading data. Read channel optimization is a channel parameter estimation procedure in which a specific pattern is written in a channel optimization position of a disk, the pattern is iteratively read, while varying combinations of channel parameters to be optimized, and a total number of errors is calculated during a read operation.
However, the optimization confined to read channel parameters has limits in maximizing drive performance because a specific pattern cannot reliably be written by a head on a channel optimization position of a disk with non-optimized write channel parameters. Hence, write channel parameter optimization should precede read channel parameter optimization.
Further, if head noise and external stresses cause non-repeatable runout, the above read channel parameter optimization method results in a high error rate for a predetermined time period.
In conclusion, the above read channel parameter optimization method cannot optimize read channel combinations due to its distinctive shortcomings of noise generated from the disparity in number between data writes and data reads, the resulting increase of errors, and thus cannot accurately estimate an error rate.
The following patents each discloses features in common with the present invention but do hot teach or suggest the specifically recited technique for optimizing read/write channel parameters of the present invention: U.S. Pat. No. 5,831,782 to Kohno et al., entitled Method And Apparatus For Supplying Optimal Bias Current To A Magnetic Head, U.S. Pat. No. 5,726,821 to Cloke et al., entitled Programmable Preamplifier Unit With Serial Interface For Disk Data Storage Device Using MR Heads, U.S. Pat. No. 4,821,125 to Christensen et al., entitled Compensation Of Write Current And Delta-V For Recording Component And Radial Position, U.S. Pat. No. 5,121,262 to Squires et al., entitled Disk drive System Employing adaptive Read/Write Channel Controls And Method Of Using Same, U.S. Pat. No. 5,408,367 to Emo, entitled Method Of Optimizing Operation Of disk Drive, U.S. Pat. No. 5,258,876 to Danner et al., entitled Zone Bit Recording With Write Compensation, U.S. Pat. No. 5,537,264 to Pinteric, entitled Method For Optimally Selecting Media Transfer Rates For Different Data Heads Based On Individual Data Head Performance, U.S. Pat. No. 5,430,581 to Moribe et al., entitled Method And Apparatus For Optimizing The Recording and Reproducing Of Information From Magnetic Disks, U.S. Pat. No. 5,657,176 to Moribe et al., entitled Method And Apparatus For Optimizing The Recording And Reproducing Of information From Magnetic Disks, U.S. Pat. No. 5,771,131 to Pirzadeh, entitled Tracking In Hard Disk Drive Using Magnetoresistive Heads, U.S. Pat. No. 5,107,378 to Cronch et al., entitled Adaptive Magnetic Recording And Readback System, U.S. Pat. No. 5,262,907 to Duffy et al., entitled Hard Disc Drive With Improved Servo System, U.S. Pat. No. 5,121,260 to Asakawa et al., entitled Read Channel Optimization System, U.S. Pat. No. 5,610,776 to Oh, entitled Method Of optimizing Read Channel Of disk Drive Recording Apparatus By Using Error Rate, U.S. Pat. No. 5,600,500 to Madsen et al., entitled Performance Based Write Current Optimization Process, U.S. Pat. No. 5,687,036 to Kassab, entitled Selection Of Optimum Write Current In A Disc Drive To Minimize The Occurrence Of Repeatable Read Errors, and U.S. Pat. No. 5,774,285 to Kassab et al., entitled Selection Of optimal Read/Write Channel Parameters In A Hard Disc Drive.